A developmental neurotoxicity study will provide information on the effects of repeated exposure to a substance during in utero and early postnatal development. The test substance is administered daily, generally orally, to mated females (rats are preferred) from the time of implantation (GD 6) throughout lactation (PND 21). At least three dose levels and a concurrent control should be used and a total of 20 litters are recommended at each dose level. Dams are tested to assess effects in pregnant and lactating females and may also provide comparative information. Offspring are randomly selected from within litters for neurotoxicity evaluation. All dams and all offspring should be carefully observed at least once daily with respect to their health condition, including morbidity and mortality. The evaluation consists of observations to detect gross neurologic and behavioural abnormalities, and the evaluation of brain weights and neuropathology during postnatal development and adulthood. The report should include the body weight, the food/water consumption; the detailed clinical observations, the necropsy findings, a detailed description of all behavioural, the number of animals at the start and at the end of the study and the toxic response data by sex and dose level.